Induction heating is a non-contact method of selectively heating inducing a magnetic field into the material to be heated. Because induction heating uses alternating magnetic fields, it is only capable of heating electrically-conductive materials; i.e. the eddy current effect. Induction heating has been used in industry for may years, mainly for the purpose of heating metals, e.g. in annealing and soldering. However, figures of merit for induction heating of solid pieces of metal are significantly different from those for heating typical catalysts.
Hydrogen cyanide, hereinafter HCN, is an important chemical with many uses in the chemical and mining industries. For example, HCN is a raw material for the manufacture of adiponitrile for use in nylon; acetone cyanohydrin to make methyl methacrylate for acrylic plastics; sodium cyanide for use in gold recovery; and intermediates in the manufacture of pesticides, agricultural products, chelating agents, and animal feed. HCN is a highly toxic liquid boiling at 26 degrees C. and as such, is subject to stringent packaging and transportation regulations. In some applications, HCN is needed at remote locations distant from large scale HCN manufacturing facilities. For example, it is used in preparing cyanide derivatives on sites at which the derivatives will be used. Shipment of HCN to such locations involves major hazards. Local production of the HCN at sites at which it is used avoids the transportation hazards. However, this clearly requires the installation of a large number of small production facilities and is an expensive option.
As a rule, HCN is produced when compounds containing hydrogen, nitrogen, and carbon are brought together at high temperatures, with or without a catalyst. HCN is most commonly produced industrially by either the exothermic Andrussow process and the endothermic Degussa process or, to a lesser extent, the endothermic Shawinigan process. Other processes for making HCN that have not been significantly exploited commercially, due primarily to unsatisfactory economics, include formamide decomposition, methanol ammonolysis, and reaction of acid with sodium cyanide. HCN is also produced as a by-product in the Sohio process for the synthesis of acrylonitrile from propene and ammonia.
In all of the foregoing processes, the emerging product stream must be promptly cooled below about 300 degrees C. to prevent thermal degradation from occurring. Additionally, unreacted ammonia, termed "ammonia breakthrough", must be removed since it can catalyze the polymerization of HCN, a process that can lead to explosions. In large plants the ammonia is recovered and recycled, in smaller units it may be burned or removed as ammonium sulfate, although the disposal processes involve environmental concerns over nitrogen oxide emissions and ammonium sulfate disposal respectively.
While it is known that HCN can be produced by the reaction of CH.sub.4 and NH.sub.3 in the presence of a Pt group metal catalyst, there is still a need to improve the efficiency of that process and related ones so as to improve the economics of HCN production, especially small scale production. It is particularly important to minimize energy use and ammonia breakthrough while maximizing the HCN production rate versus the amount of precious metal catalyst. Furthermore it is desired to improve activity and life of catalysts used in this process. Significantly, a large part of the investment in production of HCN is in the platinum group catalyst. The present invention accomplishes these desiderata.